Various agents such as reverse transcriptase inhibitors and proteinase inhibitors have been developed for the treatment of HV-infection. Multidrug therapy using three to four kinds of these agents together (so-called highly active antiretroviral therapy: HAART) have been effective for HIV-infection patients to enable the blood HIV concentration to be remarkably reduced and the number of CD4 lymphocytes to be improved. However, HAART has been unable to eliminate latently infected cells and to completely cure the HIV-infected patients. Consequently, it has been a problem that HIV is revitalized in the latently infected cells and proliferate when medication is suspended.
While it has been reported that immunological response to the HIV is sometimes efficiently induced by intermittently repeating interruption and resuming of HAART, the method has not been recognized to be a reliable therapy. However, this result indicates the importance of the immunological response to HIV.
While human monoclonal antibodies that specifically react with the HIV-infected cells have been prepared by humanizing antibodies by gene recombination, they are IgG type antibodies. While the IgG antibody is a neutralizing antibody that inhibits HIV infections, it cannot impair infected cells.
While there are species-specific complement control membrane factors (such as DAF, decay accelerating factor; MCP, membrane cofactor protein; and HRF20, 20 kDa homologous restriction factor) on human cell membranes, they can induce no cytolysis reaction via complement reactions for preventing reactions among homologous human complements.
On the other hand, it was found that IgM antibodies in human serum that react with the HIV-infected cells are able to yield the cytolysis reaction of the HIV-infected cells via the human complement by overcoming the complement control membrane factors. It was revealed that the IgM antibody can exhibit such action as described above against gangliosides such as GM2 and Gg4 whose expression is enhanced by HIV-infection (Japanese Patent Application Laid-Open No. 9-227409, page 2, paragraph [0009]).
L55 has been reported as the human IgM monoclonal antibody against GM2 of the gangliosides, wherein L55 is produced by immortalizing human B lymphoblast strain with EB virus. The HIV-infected cells after treating with this human IgM monoclonal antibody have been found to yield cytolysis via a reaction with the human complement. However, since the L55 antibody is not specific to the HIV-infected cells, it may react with normal cells other than the HIV-infected cells.